Many processing steps in semiconductor manufacture and micromachining require that a thin film of metal is deposited upon a surface in a controlled and precision manner. Thin electrically conducting films—also named interconnects—cover approximately 10% of the total surface of the substrate in OLED technology.
One method for depositing a thin metal film uses laser-thermal or photo-decomposition of organometallic gases above substrate surfaces. This continuous laser-thermal method is currently used for some metallization applications, yet in practice it suffers from at least three disadvantages. First, metal atoms generated in the gas phase above the substrate tend to spread over the surface away from the region of decomposition. Second, the process is relatively slow. Third, only those metals having an appropriate organometallic gas can be used. These problems make rapid, precise metallization by this method impractical for many microelectronics and microstructuring applications. Furthermore, this method inherently has an associated environmental problem of requiring safe handling and disposal of some toxic organometallic gases and structures.
In another method, the entire substrate surfaces are coated with the electrically conducting film material using the sputter method. Then wet chemical etching or an ablative laser method are used to expose the desired thin film geometry on the substrate. The etching solutions used however are problematic under toxicological and environmental protection aspects and, just like the proportions of the interconnect material which are deposited on machine components, can hardly be recycled.
A further method for producing electrical interconnects on surfaces is the laser sintering of nano-particles which in a dispersion are applied with an inkjet method. Neither the structure sizes and geometries nor the process speed with this method have been adequate for industrial mass production in OLED technology up to now. In addition, the substrate can be damaged by thermally induced cracks during the laser process.